Core complex type structures are common in continental margins. Recent studies have proposed exhumation of deeper crustal and mantle levels during extension of the continental margin along the Northern South China Sea (NSCS) in a core complex mode. Here, we present high-resolution seismic profiles across different sections of the NSCS that allow us to observe two types of core complex systems. The Kaiping Rift and eastern Baiyun Rift are characterized by a sub-horizontal Moho and exhumation of ductile deeper crust beneath an extremely thinned brittle upper crust. The central Baiyun Rift in contrast is marked by homogeneous thinning of the entire crust that is floored by mantle unroofing with a concave-down Moho geometry. While the former type, referred to as crustal core complexes, coincides with relatively intense syn-rift magmatism, the latter, referred to as mantle core complexes, is marked by limited magmatism. Consistently, basin subsidence rates are lower over crustal core complexes than mantle core complexes. Compared to mantle core complexes at the magma-poor Iberian margin, the widely distributed crustal core complexes in the NSCS indicate higher geotherms and more intense magmatism during extension of the continental lithosphere. We propose that the continental core complexes observed at the NSCS represent a typical outcome of extension of a gravitationally unstable lithosphere.

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大陆核心杂岩对裂谷模式的影响：来自南海北缘多道地震数据的见解

核心复杂型构造在大陆边缘很常见。最近的研究提出，在沿着南海北部（NSCS）的大陆边缘扩展过程中，以核心复合体模式折返了更深的地壳和地幔层。在这里，我们展示了 NSCS 不同部分的高分辨率地震剖面，使我们能够观察两种类型的核心复杂系统。开平裂谷和白云裂谷东部的特征是亚水平莫霍面和极薄脆性上地壳下的延性深层地壳折返。相比之下，中央白云裂谷的特点是整个地壳均匀变薄，其底部是具有凹形莫霍面几何形状的地幔脱顶。前一种类型（称为地壳核杂岩）与相对强烈的同裂谷岩浆作用相一致，而后者（称为地幔核杂岩）的特点是岩浆作用有限。一致地，地壳核复合体的盆地沉降率低于地幔核复合体的沉降率。与贫岩浆伊比利亚边缘的地幔核杂岩相比，NSCS广泛分布的地壳核杂岩表明大陆岩石圈伸展期间地温更高，岩浆活动更强烈。我们认为，在 NSCS 观测到的大陆核心复合体代表了重力不稳定岩石圈扩张的典型结果。